Comparison study from sputtering, sol-gel, and ALD processes developing embedded thin film capacitors

Three methods for fabricating thin film capacitors are investigated using sputtering, sol-gel, and atomic layer deposition (ALD) techniques for advanced packaging applications for embedded capacitors. In particular, the microstructures and the electrical properties of ceramic oxide films Au/Ti/Al₂O₃ for ALD are being studied while ferroelectric thin films Au/Ti/BaTiO₃ for sol-gel and Cu/Ba_{1 - x}Sr_xTiO₃ for sputtering are being discussed in detail. The upper Au/Ti electrode layer is deposited by dc magnetron sputtering on top of Al₂O₃ (ALD process) and on BT layer to complete the Au/Ti/BaTiO₃/Ni/Cu/FR4/Cu (sol-gel process) structure respectively whereas Cu is deposited by sputtering on top of the BST layer to complete the Cu/BaTiO₃/Cu/SiO₂ /Si (sputtering process). After a careful comparison is done, ALD for the Al₂O₃ thin film seems to show the most promising process for its low temperature at 150 degC and for its electrical properties like a capacitance of 0.88nF/mm² with less then plusmn2% tolerances, a dissipation factor of less than 0.018, and a low leakage current less than 0.1 muA/cm² at 4V